一個簡易的選項卡鏤空的分段控制器：
內(nèi)部使用UICollectionView實現(xiàn)，可以計算出當(dāng)前顯示的控制器視圖的下標(biāo)，以及將要顯示控制器視圖的下標(biāo)。底部選項紅線隨title寬度變化。

效果圖

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    if (scrollView == self.contentCollectionView) {
        // 計算將要顯示的控制器視圖下標(biāo)
        NSInteger contentOffset_x = (NSInteger)ABS(self.selectedIndex * scrollView.frame.size.width - scrollView.contentOffset.x);
        if (scrollView.contentOffset.x < self.selectedIndex * scrollView.frame.size.width) { // ←
            self.willSelectIndex = self.selectedIndex - ceil(contentOffset_x/scrollView.frame.size.width);
        }else { // →
            self.willSelectIndex = self.selectedIndex + ceil(contentOffset_x/scrollView.frame.size.width);
        }
        self.segmentBar.selectedItemContentOffset_x = scrollView.contentOffset.x;
        [NSObject cancelPreviousPerformRequestsWithTarget:self];
        [self performSelector:@selector(scrollViewDidEndScrollingAnimation:) withObject:self.contentCollectionView afterDelay:.1];
    }
}

- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
{
    if (scrollView == self.contentCollectionView) {
        [NSObject cancelPreviousPerformRequestsWithTarget:self];
        NSLog(@"scroll end");
        // 計算已經(jīng)顯示的控制器視圖下標(biāo)
        self.selectedIndex = (NSInteger)(scrollView.contentOffset.x / scrollView.frame.size.width);
        self.willSelectIndex = self.selectedIndex;
    }
}

demo地址